The present invention relates to regulated DC to DC converters and voltage regulation methods, and more particularly to a circuit in which a major portion of the prime power is processed through a square wave inverter, and in which regulation is achieved by processing a small portion of the prime power through a pulse width modulated switching regulator.
Given a regulated prime power source, power can be processed to useful voltage levels with a basic square wave inverter and transformer. This assumes a DC source and DC loads. The square wave inverter is very efficient and is very light in weight for a given power processed.
However, when the prime power source is not regulated, and there is a requirement for regulated voltage outputs, a number of options are available, including the following: (1) to regulate the prime power; (2) to regulate the output; or (3) to operate an inverter in a non-square wave fashion that employs pulse width modulation techniques to achieve regulation. Options (1) and (2) are occasionally selected, usually at a cost of efficiency and weight. Option (2) is rarely selected where high voltage is required. Option (3) is generally selected where weight and efficiency are a concern, especially if high voltages are required as outputs.
A number of circuits falling in the category of option (3) are known and used to regulate power for traveling-wave tubes in space applications, for example. One novel and efficient arrangement is disclosed in U.S. Pat. No. 3,925,715, entitled "Regulated DC to DC Converter", issued to H. D. Venable on Dec. 9, 1975. This converter circuit employs pulse width modulation in a manner such that a significant amount of ripple current is produced. The filter elements required in this circuit can be large and relatively lossy, even though this circuit is one of the most efficient and lowest weight arrangements currently in use.